GDT_G23 - Literally just answered that in the previous post. I triggered it by going to the Principal's office (Nicholas) then back to the classroom.
If you are a high enough Patron to have access to the latest content, you
really should have the foresight to realise that the walkthrough hasn't had the time to be written yet, so any new content explicitly requires experimentation in order to find out what the trigger is. So go for it - EXPERIMENT!! FOR SCIENCE!!!!!
Keep in mind people, this is a "Work in Progress". Things will change, and may not be as expected. Which is why I tend not to answer people who ask "How do I do this?". Between versions it may change, so how the hell are
we meant to know! That really is a question to ask the dev. The rest of us are just guessing (unless you have access to the code, but DS seems to be particularly careful about that)
But I will post tips I have noticed that help, for those that are less experimental. I don't even claim to know the answers - I only discovered the game a little while ago